Injection moulding die locking and opening device

ABSTRACT

A locking and opening device for an injection moulding die, particularly for processing highly liquid melted plastic material, provides a technically simple, low cost mechanism to lock the die and limit elements located above workbench level or mould level, when the device is arranged vertically. To achieve this, clamping pins hold one moulding die in a closed position in relation to an overlying moulding die and which can be axially displaced into a closed or open position by means of a sliding element associated with each clamping pin.

BACKGROUND

1.0 Field of the Invention

This invention relates to a mechanism for locking and opening aninjection mold, more particulary for processing low-viscosity moltenplastic.

2.0 Discussion of Related Art

Injection molds are available in various forms. For example, it isknown, even in the processing of low-viscosity molten plastic, that theupper half of a mold, for example, can be moved downwards by a closingcylinder onto the lower half, and then held under pressure in the closedposition, with pressures of 6,000 to 7,500 N being applied. It is alsopossible to assemble a casting mold by hand via a drawer system and theninsert it into clamps which lock the mold halves and fix them inrelation to an injection nozzle.

It is also known that mold halves can be guided on slide elements foropening and closing, and kept in the closed position by toggle levers.If closing cylinders, toggle levers or the like are used, comparativelyhigh outlay for equipment is involved. In addition, space has to becreated for the closing mechanism, for example above a worktable, if theupper mold half is moved by a cylinder into the working position on thelower half and held in that position.

3.0 SUMMARY OF THE INVENTION

An object of the present invention is to provide a technically simpleinexpensive mold locking mechanism for substantially eliminating theneed for elements above the worktable level or in front of a verticallyarranged mold plane.

The above object and other objects are provided in accordance with theinvention by clamping pins which hold one part of the mold in the closedposition relative to the other part and which are each designed foraxial displacement by an associated slide element into either a closedposition, or into an open position.

The locking of the mold halves relative to one another by thecombination of clamping pins and slide elements actuating the clampingpins the other hand provides for a very simple construction.

The combination of clamping pins and slide elements fixing the clampingpins makes the closure independent of the injection pressures applied.The locking mechanism according to the invention is capable ofwithstanding very high pressures.

In one embodiment of the invention, the two slide elements are combinedto form a forked slide which is mounted for displacement by a driveelement, more particularly a pneumatic cylinder. Pneumatic cylinderswith a comparatively low closing pressure may be used in accordance withthe invention because the pneumatic cylinders are not required to applya closing pressure. This is done via a cable element or directly throughthe slide elements.

In a preferred embodiment of the invention, one part of the mold isdesigned as a lower mold half positioned at worktable level while theother part of the mold is designed as an upper mold half, the forkedslide and its drive being arranged below worktable level.

This arrangement enables the working plane to be kept substantially freefrom mold closing or actuating elements so that considerable freedom ofmovement is available as there is no need for conventional positivelocking mechanisms.

In another embodiment of the invention, the slide elements are formedwith longitudinal slots which merge into a widened region that allows ahead element on each clamping pin to pass through.

Another particularly advantageous embodiment is characterized in that,on one side, each slide element has a ramp which moves the clamping pininto the closed position and, on the other side, a ramp which moves theclamping pin into the open position.

This construction according to the invention provides not only foroptimal closing of the mold halves, but also for simple opening becausethe mold automatically undergoes a minimal lifting movement via the rampfor movement into the opening position which considerably simplifiesremoval of the molding.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is explained in more detail in the following withreference to the accompanying drawings, in which like items areidentified by the same reference designation, wherein:

FIG. 1 is a side elevational view, partly in section, with the injectionmold in the closed position.

FIG. 2 is a side elevational view, partly in section, with the injectionmold in the open position before the upper mold half is removed.

FIG. 3 is a partial cross-sectional view taken perpendicularly of thesections of FIGS. 1 and 2.

FIG. 4 is a view from above in the direction of arrow IV in FIG. 1partly broken away.

DETAILED DESCRIPTION OF THE INVENTION

In the illustrated examples, the mechanism generally denoted by thereference 1 is formed by a mold lower half 2 and a mold upper half 3with the parting plane at the level of a worktable 4 and by a pneumaticcylinder 5 and a nozzle 6 for injecting plastic into the mold lowerhalf.

In the illustrated example, two clamping pins 7 are provided in the moldupper half 3, the shank 8 of each clamping pin passing slidingly throughthe mold lower half 2. The clamping pins 7 comprise a guide neck 9 and ahead 10, the guide neck 9 being guided in a slot guide 11 of a slideelement generally denoted by the reference 12, (see FIGS. 3 and 4) theslot 11 merging into a widened opening 13 which allows the head 10 topass through.

Slide elements 12 are provided for actuating the clamping pins 7, beingcombined to form a fork (see FIG. 4) and designed for displacement inthe direction of the double arrow 15 (FIG. 1) by the hydraulic cylinder5.

As can be seen from FIGS. 1 and 2 in particular, each slide element 12has an upper ramp 16 and a lower ramp 17 of which the effect is that thehead 10 in FIG. 1 is moved downwards in the direction of the arrow 18via the lower ramp 17 and upwards in the direction of the arrow 19 viathe ramp 16. In the event of a downward movement in the direction ofarrow 18, the two mold halves 2 and 3 are locked. If the clamping pin 7is moved upwards in the direction of arrow 19 via the ramp 16, the moldhalves move slightly, for example by only 2 mm, into the open positionshown in FIG. 2. At the same time, the molding is loosened.

If the ram 14 (see FIG. 4) is located in the end position shown in FIG.2, the head 10 aligns with the widened part 13 of the slot 11 so thatthe upper mold half 3 can be lifted upwards without difficulty either byhand or automatically.

The embodiment of the invention described in the foregoing can of coursebe modified in many respects without departing from the basic concept.For example, the two ramps 16 and 17 with the slot guide 11 and thewidened opening 13 may be arranged on segments of a rotatable disk whichis rotated below the worktable level. Other modifications are alsopossible, which modifications are meant to be covered by the spirit andscope of the appended claims.

What is claimed is:
 1. A mechanism for closing and opening an injectionmold, for processing low-viscosity molten plastic, comprising: a moldincluding an upper half mold section separable from a lower half moldsection, each having top and bottom faces; first and second clampingpins that are vertically oriented and spaced apart, each having an upperportion retained in said upper half mold section, a mid-shank portionpassing slidably through said lower half mold section, a narrowed guideneck portion immediately following said mid-shank portion and protrudingfrom the bottom face of said lower half mold section, and a head portionfollowing and terminating the associated narrower mid-shank portion;first and second slide elements spaced apart and horizontally movablerelative to said first and second clamping pins, said first and secondslide elements each including a longitudinal slot portion slidably andcaptively retainable on said guide neck between said mid-shank portionand said head portion of an individual one of said first and secondclamping pins, respectively; and said first and second slide elementseach further including top and bottom portions, an upper ramp on the topportion, and a lower ramp on the bottom portion displaced from thelocation of the upper ramp, whereby said first and second slide elementsare moved in one direction for causing respective said lower ramps toengage the heads of said first and second clamping pins, respectively,for moving the latter vertically downward to move the upper half moldsection into locking engagement with the lower half mold section, andwhen thereafter said first and second slide elements are moved in anopposite direction respective said lower ramps move away from associatedhead portions of said first and second clamping pins, followed byrespective said upper ramps engaging ends of the associated mid-shankportion of said first and second clamping pins, respectively, for movingthe latter vertically upward to move the upper half mold section awayfrom the lower mold section.
 2. A mechanism as claimed in claim 1,wherein said first and second slide elements consist of slide armsconfigured to form a forked slide which is mounted for displacement by adrive element.
 3. A mechanism as claimed in claim 2, wherein said lowerhalf mold section is positioned at a worktable level, and the upper halfmold section, with the forked slide and its drive are arranged belowworktable level.
 4. A mechanism as claimed in claim 2, wherein thelongitudinal slots of the first and second slide elements each mergeinto a widened region that allows said head portion on each of saidfirst and second clamping pins respectively, to pass through.
 5. Amechanism as claimed in claim 2, wherein said drive element includes apneumatic cylinder.
 6. A mechanism as claimed in claim 3, wherein thelongitudinal slots of said first and second slide elements each mergeinto a widened region that allows said head portion on each of saidfirst and second clamping pins to pass through.